1. Field of the Invention
This invention relates to a process and apparatus for precipitating insoluble solids from a liquid solution and a reactant which react to form the solids and, more particularly to a process and apparatus for precipitating insoluble saccharate from an aqueous sucrose solution.
2. Prior Art
Precipitation of insoluble solids from a liquid solution by the addition of a reactant is commonly facilitated by means of mechanical agitation of the solution and the reactant. For example, in the sugar industry, the formation of insoluble saccharates is commonly accomplished by such a process.
In the common commercial processes of recovering sugar from sugar beets or the like, the beets are cut into thin slices ("cossettes"), the cossettes are extracted with hot water to produce a sucrose-containing diffusion juice, and then the diffusion juice is processed to produce crystalline sugar and a molasses solution. Additional crystalline sugar may be recovered from the molasses solution by the "Steffen Process" which comprises the steps of: (1) diluting the molasses solution with water to produce a solution containing about 6% sucrose, (2) adding finely powdered quicklime (CaO) to the solution with violent agitation to precipitate insoluble saccharate, (3) filtering the solution (about 90% of the sugar is recovered in the precipitate with about 10% portion remaining in the filtrate), (4) heating the filtrate to about 90.degree. C to form additional precipitate (contains about 6.5% of the sugar originally present in the molasses solution, and (5) recovering the additional precipitate by settling and filtration. The precipitated saccharate may then be slurried in water and reprocessed for recovery of additional crystalline sugar.
In the prior art, various methods and apparatus have been used to facilitate the addition of quicklime to the molasses solution to ensure a uniform reaction by thorough mixing of the quicklime and the molasses solution by mechanical agitation. The prior art processes have also utilized mechanical cooling in the reaction chamber to dissipate the heat of dissolution of the quicklime in the solution and the heat of reaction of the CaO with the sucrose, to obtain precipitation of the saccharate. The prior art processes have further required a very dilute molasses solution (e.g., a maximum sucrose concentration of about 6%) for efficient processing.